This invention relates to a method of and apparatus for determining motility.
A sophisticated control system governs the strength and sequence of contractions of the stomach and bowel. The integrity of this control system is vital to ensure that food contents are adequately mixed with the digestive juices and are pushed along the length of the gut at the correct rate to allow adequate digestion and absorption of nutrients. This activity of the stomach and bowel (i.e. the strength and sequence of contractions) is known as its motility. Because the control system is complex, breakdowns occur frequently and disorders of gastrointestinal motility are common. The severity of these disorders varies from that which is uniformly fatal (fortunately uncommon) to that which causes chronic and disabling symptoms.
It has been estimated that approximately 90% of patients who have been referred to any gastrointestinal clinic suffer from some form of motility disorder. In this connection see Loof L., Adani H. O., Agera S.I., et al. the Diagnosis and Therapy Survey (Oct. 1987-March 1983). Health Care consumption and current drug therapy in Sweden. Scand. J. Gastroenterol, 20 (Suppe 109): 29-35 (1985). Although motility disorders are common, they are poorly understood probably because the techniques for their steady are limited. These techniques involve measurement of pressure changes inside the gut, by the swallowing of one or more tubes or radio pressure pills. Since the gastrointestinal tract is 26 feet long, the techniques only provide information at few loci along its length. The techniques are thus difficult and uncomfortable and are suitable only for small numbers of patients at specialist centres.
Contractions of the gastrointestinal tract are associated with the release of vibrational energy, both within and outside the acoustic spectrum. This energy may be captured, measured and analyzed. That which lies within the acoustic spectrum may be detected by a stethoscope as bowel sounds and previous investigators have been concerned only with the capture of bowel sounds. In early studies, sounds were captured over short intervals of time and all characterization of the signal was subjective or qualitative. For example, readers are referred to: 1) Du Plessis, D. J. Clinical observations on intestinal motility, S. Afr. Med J. 28: 27-33 (1954), 2) Wells C., Rawlinson K., Tinckler L., Jones H. and Saunders J. Illeus and postoperative intestinal motility, Llancet 2: 136-137 (1961), 3) Baker L. W. and Dudley H.A.F. Auscultation of the abdomen in surgical patients. Lancet 2: 517-519 (1961), 4) Horn G.E. and Mynors J. M. Recording the bowel sounds. Med & Biol Engin. 205-209 (1955).
Several studies carried out some crude signal analysis, but recording times were short and results inconclusive. See 1) Farrar J. T. and Ingelfinger F. J. Gastrointestinal motility as revealed by a study of abdominal sounds, Gastroenterology 29: 789-800 (1955), 2) Watson W.C. and Know Elizabeth, C. Phonoenterography: the recording and analysis of bowel sounds, Gut 8: 88-94 (1967), 3) Politzer J. P., Devoede E., Vasseur C., et al., the genesis of bowel sounds: influence of viscus and gastrointestinal content, Gastroenterology 71: 282-285 (1976).
All of the previous techniques have relied upon microphones for signal capture, with limited success. Microphones essentially address the acoustic spectrum and in general they depend upon an air interface for conversion of vibrational energy to an electronic signal. Hence, they are sensitive to any other vibrational interference, for example background noise, which is transmitted through air.